Variable Access

The Variable Access pane displays global variables (and local static variables). For each global variable, the pane lists all functions and tasks performing read/write access on the variables, along with their attributes, such as values, read/write accesses and shared usage.

To open this pane, in the Polyspace^® desktop user interface, select the button on the Result Details pane.

For each variable and each read/write access, the Variable Access pane contains the relevant attributes. For the variables, the various attributes are listed in this table.

Attribute	Description
Variables	Name of Variable
File	Source file containing variable declaration
Values	Value (or range of values) of variable This column is empty for pointer variables.
# Reads	Number of times the variable is read
# Writes	Number of times the variable is written
Written by task	Name of tasks writing on variable
Read by task	Name of tasks reading variable
Protection	Whether shared variable is protected from concurrent access (Filled only when Usage column has entry, Shared) The possible entries in this column are: Critical Section: If variable is accessed in critical section of code Temporal Exclusion: If variable is accessed in mutually exclusive tasks For more details on these entries, see Multitasking.
Usage	Shared, if variable is shared between tasks; otherwise, blank
Line	Line number of variable declaration
Col	Column number (number of characters from beginning of line) of variable declaration
Data Type	Data type of variable (C/C++ data types or structures/classes)

Double-click a variable name to view read/write access operations on the variable. The arrowhead symbols and in the Variable Access pane indicate functions performing read and write access respectively on the global variable. Likewise, tasks performing read and write access are indicated by the symbols and respectively. For further information on tasks, see Tasks (-entry-points).

For access operations on the variables, the various attributes described in the pane are listed in this table.

Attribute	Description
Variables	Names of function (or task) performing read/write access on the variable
Values	Value or range of values of variable in the function or task performing read/write access This column is empty for pointer variables.
Written by task	Only for tasks: Name of task performing write access on variable
Read by task	Only for tasks: Name of task performing read access on variable
Line	Line number where function or task accesses variable
Col	Column number where function or task accesses variable
File	Source file containing access operation on variable If this column contains the name __polyspace__stdstubs.c, it indicates that the variable is accessed inside a Standard Library function.

For example, consider the global variable, SHR2:

The function, Tserver, in the file, tasks1.c, performs two write operations on SHR2. This is indicated in the Variable Access pane by the two instances of Tserver() under the variable, SHR2, marked by . Likewise, the two write accesses by tasks, server1 and server2, are also listed under SHR2 and marked by .

The color scheme for variables in the Variable Access pane is:

• Black: global variable.

• Orange: global variable, shared between tasks with no protection against concurrent access.

• Green: global variable, shared between tasks and protected against concurrent access.

• Gray: global variable, declared but not used in reachable code.

If a task performs certain operations on a global variable, but the operations are in unreachable code, the tasks are colored gray.

The information about global variables and read/write access operations obtained from the Variable Access pane is called the data dictionary.

You can also perform the following actions from the Variable Access pane.

•  View Access Graph

  View the access operations on a global variable in graphical format using the Variable Access pane. Select the global variable and click .

  Here is an example of an access graph:

  

•  View Structured Variables

  For structured variables, view the individual fields from the Variable Access pane. For example, for the structure, SHR4, the pane displays the fields, SHR4.A and SHR4.B, and the functions performing read/write access on them.

  

•  View Operations on Anonymous Variables

  You can view operations on anonymous variables. For example, consider this line of code that declares an unnamed union with the variable at an absolute address:

  union {char, c; int i; } @0x1234;

  When you analyze the preceding code and specify the iar compiler, the unnamed variable at 0x1234 appears in the Variable Access pane with a name that starts with pstanonymous.

  

•  View Access Through Global Pointers

  View access operations on global variables performed indirectly through global pointers.

  If a read/write access on a variable is performed through global pointers, then the access is marked by (read) or (write). Access through local pointers is shown like any other direct access.

  For instance, in the file, initialisations.c, the variable, arr, is declared as a pointer to the array, tab.

  

  In the file main.c, tab is read in the function, interpolation(), through the global pointer variable, arr. This operation is shown in the Variable Access pane by the icon.

  During dynamic memory allocation, memory is allocated directly to a pointer. Because the Values column is populated only for non-pointer variables, you cannot use this column to find the values stored in dynamically allocated memory. Use the Variable Access pane to navigate to dereferences of the pointer on the Source pane. Use the tooltips on this pane to find the values following each pointer dereference.

•  Show/Hide Callers and Callees

  Customize the Variable Access pane to show only the shared variables. On the Variable Access pane toolbar, click the Non-Shared Variables button to show or hide non-shared variables.

•  Hide Access in Unreachable Code

  Hide read/write access occurring in unreachable code by clicking the filter button .

•  Limitations

  You cannot see an addressing operation on a global variable or object (in C++) as a read/write operation in the Variable Access pane. For example, consider the following C++ code:

  class C0 
  { 
  public: 
    C0() {} 
    int get_flag() 
    { 
      volatile int rd; 
      return rd; 
    } 
    ~C0() {} 
  private: 
    int a;                /* Never read/written */ 
  }; 
  
  C0 c0;                  /* c0 is unreachable */ 
  
  int main() 
  { 
    if (c0.get_flag())    /* Uses address of the method */ 
      { 
        int *ptr = take_addr_of_x(); 
        return 1; 
      } 
    else 
      return 0; 
  }

  You do not see the method call c0.get_flag() in the Variable Access pane because the call is an addressing operation on the method belonging to the object c0.